1. Field of the Invention
Example embodiments generally relate to a recording sheet feeder and an image forming apparatus, and more particularly, to a recording sheet feeder for feeding a recording sheet, and an image forming apparatus including the recording sheet feeder.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording medium (e.g., a recording sheet) according to image data. Thus, for example, an image forming device forms an image according to the image data. The image is transferred onto a recording sheet fed by a recording sheet feeder toward the image forming device.
The recording sheet feeder typically includes a recording sheet tray for loading recording sheets, a recording sheet tray moving mechanism for lifting and lowering the recording sheet tray, and a feed roller for feeding the recording sheets loaded on the recording sheet tray toward the image forming device. As the height of the stack of recording sheets placed on the recording sheet tray decreases after the feed roller feeds successive recording sheets and the feed roller starts to separate from an uppermost recording sheet of the recording sheets placed on the recording sheet tray, the recording sheet tray moving mechanism lifts the recording sheet tray upward so that the uppermost recording sheet remains in contact with the feed roller.
The recording sheet feeder may include a motor and a lift lever that function as the recording sheet tray moving mechanism for lifting and lowering the recording sheet tray. The direction of rotation of the single motor is switched to lift the recording sheet tray via the lift lever when a sensor detects that the number of recording sheets placed on the recording sheet tray has decreased. Thereafter, the feed roller rotates and feeds the recording sheets placed on the recording sheet tray toward the image forming device.
With such a structure, the recording sheet tray is raised whenever the number of recording sheets placed on the recording sheet tray decreases. It is to be noted that the feed roller does not rotate while the recording sheet tray is being raised. When the rotation of the feed roller is interrupted frequently due to repeated lifting of the recording sheet tray, productivity of the image forming apparatus may deteriorate.
Alternatively, the recording sheet feeder may include a pressing plate which is lifted and lowered to press the recording sheets against the feed roller and two cams mounted axially on both ends of a feed roller driving shaft to lift and lower the pressing plate. As the feed roller is also mounted on the feed roller driving shaft, rotation of the feed roller is interlocked with driving of the cams to feed the recording sheets.
However, the interlocked rotation of the feed roller may restrict the length of the recording sheets to be fed. Moreover, a user needs to remove the two cams from the feed roller driving shaft to replace the feed roller with a new one, complicating maintenance.